1. Field of the Invention
The present invention generally relates to a method for playing an optical disc, in particular, to a method for playing a non-finalized optical disc.
2. Description of Related Art
According to the current specification of optical discs, a complete optical disc has a lead-in zone, a lead-out zone, and a data zone. When a read-only optical disc drive first reads an optical disc, the read-only optical disc drive performs focusing and tracking actions by using the lead-in zone of the optical disc. The read-only optical disc drive can only read data recorded in the optical disc after the focusing and tracking actions are performed. The format of a digital versatile disc (DVD) will be described herein as an example. FIG. 1 illustrates the data structure of a DVD. Referring to FIG. 1, the DVD has a lead-in zone 110, a data zone 130, and a lead-out zone 150. The data zone 130 includes a file system area 132, a navigation data area 134, and a video data area 140. When a DVD recorder records a video data into a blank recordable DVD, the DVD recorder first composes the video data into a file and then burns the file into the video data area 140. After that, the DVD recorder performs a finalization action, wherein the DVD recorder composes a file system and a navigation data according to the information of the recorded video data (including the position and directory of the video data in the DVD), writes the file system and the navigation data respectively into the file system area 132 and the navigation data area 134, and then burns data into the lead-in zone 110 and the lead-out zone 150. Since the recordable DVD has been finalized, a read-only optical disc drive or a read-only disc player can track the recordable DVD by using the lead-in zone 110 thereof and play the video data recorded in the recordable DVD according to the file system recorded in the file system area 132.
As to a write-once DVD, data written into the file system area 132 and the navigation data area 134 cannot be changed, namely, the DVD cannot be used for recording any other data. Accordingly, in order to use the storage capacity of a write-once DVD efficiently, a DVD recorder reserves an area at the beginning of the data area as a file system area and a navigation data area. Besides, no finalization action is performed after each time a video data is recorded into the DVD; instead, only the video data and a file allocation data table (for example, a reserved space allocation table (RSAT) or a virtual allocation table (VAT)) are written into the DVD. The DVD is finalized only when its storage capacity is used up. The RSAT contains information of the recorded video data therefore can be used for composing the file system and the navigation data while performing the finalization action or for playing the recorded video data. FIG. 2 illustrates the data structure of a DVD which has been recorded several times. Referring to FIG. 2, the video data area 140 in the DVD contains a plurality of video data 141, 143, and 145 which are sequentially burnt into the DVD by a DVD recorder. Besides, the video data area 140 further contains a plurality of file allocation data tables 142, 144, and 146 respectively recorded after the video data 141, 143, and 145, and these file allocation data tables 142, 144, and 146 respectively record the information of the video data 141, 143, and 145.
As described above, an optical disc to which video data is recorded but the finalization action is not yet performed is referred to as a “non-finalized disc”. FIG. 3 illustrates the data structure of a DVD to which video data is recorded only once and the finalization action is not performed yet. Referring to FIG. 3, the video data area 140 in the DVD contains only a video data 141 and a RSAT 142. Since the DVD is not finalized, the lead-in zone 110, lead-out zone 150, file system area 132, and navigation data area 134 are still blank areas containing no data.
A conventional read-only optical disc drive or read-only disc player cannot track on those areas in an optical disc which contain no data. FIG. 4 is a flowchart illustrating how conventionally a read-only optical disc drive plays an optical disc. Referring to FIG. 4, an optical disc playing process is started (step S400), and a servo system of the read-only optical disc drive is turned on (step S410). While the servo system is being turned on, an optical pickup head is moved to the lead-in zone of the optical disc to perform focusing on and tracking on actions. Next, whether the servo system is successfully start-up is determined (step S420). If the servo system is successfully start-up, the read-only optical disc drive starts to read data from the optical disc (step S430). For example, the read-only optical disc drive reads the data recorded in the lead-in zone of the optical disc to obtain the storage capacity of the optical disc and reads the video data recorded in the video data area according to the file system recorded in the file system area. After reading the optical disc, the read-only optical disc drive ends the optical disc playing process (step S440). Contrarily, if it is determined that the servo system is not successfully start-up in step S420, the read-only optical disc drive determines that an operation error occurs (step S450) and terminates the optical disc playing process (step S440). As described above, when a read-only optical disc drive reads a non-finalized disc, since the optical pickup head cannot track an area containing no data, the servo system cannot be successfully start-up, and accordingly the read-only optical disc drive determines that an operation error occurs. As a result, the read-only optical disc drive cannot read the non-finalized disc. Even if the servo system in the read-only optical disc drive is successfully start-up by moving the optical pickup head to the video data area containing video data, the read-only optical disc drive cannot read data from the optical disc because the read-only optical disc drive cannot obtain the storage capacity or other information of the optical disc from the lead-in zone and the file system area. In short, a read-only optical disc drive or a read-only disc player cannot read data from any non-finalized disc.
Additionally, if the finalization action of a DVD recorder or DVD burner is terminated by an interruption (for example, a power failure or insufficient laser power etc) when an optical disc is being burnt, the optical disc cannot be read by a read-only optical disc drive or a read-only disc player because the lead-in zone and the file system area thereof contain no data.
A method and an apparatus for playing a non-finalized disc (partial disc) have been disclosed in U.S. Pat. No. 5,351,226. According to this disclosure, whether the lead-in zone of an optical disc contains data is first detected when the optical disc stays immobile, and then whether the optical disc contains data is determined and the data in the lead-in zone is re-established. The method for detecting whether the optical disc contains data includes following steps. When the optical disc stays immobile, an optical pickup head is moved to the lead-in zone of the optical disc, and a swing signal is loaded into a signal of the optical pickup head for controlling the focusing and tracking actions. Next, the optical pickup head is moved along the normal direction of the tracks on the optical disc. Meanwhile, the signal reflected by the optical disc is read and whether the swing of the signal reaches a predetermined value is detected, so that whether data has been burnt into the lead-in zone and a program area of the optical disc can be determined. If the lead-in zone of the optical disc contains no data but the program area thereof contains data, the size of each track on the optical disc is detected again in order to re-establish a table of contents (TOC) of the optical disc, and then the tracks of the optical disc are played according to the TOC.
However, in the technique described above, data in the optical disc is detected when the optical disc stays immobile. As a result, the optical pickup head cannot be positioned correctly, and accordingly data in the lead-in zone cannot be detected correctly. Besides, foregoing technique can only be applied to a compact disc digital audio (CD-DA) but not to a DVD.